Predicted Power Output of Silicon-Based Bifacial Tandem Photovoltaic Systems

Combining the higher energy yield of bifacial photovoltaic modules with the higher efficiency of silicon-based tandem devices is a promising pathway to reduce the levelized cost of electricity of photovoltaic systems. In a two-terminal bifacial tandem, the additional photon flux on the back of the bottom cell alters the current matching between the cells. This study quantifies this phenomenon, starting with spectrally resolved front and back irradiances determined from ray tracing under realistic conditions. A tandem-device model is then used to explore the impact of different scenarios on the optimal top-cell bandgap and power production. Although the energy gains from bifacial tandem systems are small, the range of suitable top-cell bandgaps is greatly broadened, thus widening the window of absorber candidates. In one exemplary case, a bifacial tandem with a top-cell bandgap as low as 1.63 eV retains the energy output of an optimized monofacial tandem with a 1.71-eV top cell.